1. Field of the Invention
The invention relates to a removable self-lubricating device for semi-trailer couplings, comprising a self-lubricating plate which is located between the support plate of the semi-trailer and the friction part of the fifth, wheel.
2. Description of the Prior Art
On tractors and semi-trailers in particular, the fifth wheel and the coupling plate have hitherto been greased with a spatula or trowel before the semi-trailer is coupled. During coupling, the grease flowed on either side of the fifth wheel, resulting in a loss of grease, a poor distribution of the grease which remained and, consequently, non-uniform and rather short-lived lubrication.
This lubrication deficiency, which hindered the free rotation of the plate relative to the fifth wheel, resulted indirectly in premature wear of the two steering pivots and of the tires and the bushes of the front springs of the tractor. This seizing also caused control problems when turning the steering wheel (oversteering).
A variety of solutions have been developed to remedy this situation by eliminating the problem of lubrication, among which there may be mentioned those described in the following patents:
EPA No. 0058732, which relates to a semi-trailer coupling comprising a fifth wheel covered with a layer of self-lubricating material, a coupling plate with a superfinished surface condition, and an intermediate steel sheet; and
EPA No. 0117319, which relates to a semi-trailer coupling whose fifth wheel is provided, over its entire surface, with a self-lubricating plate fixed by means of screws, the edges of which are protected on the back by a separate metal reinforcement.
However, the self-lubricating devices referred to above have the disadvantage that the work required to construct them is rather difficult and calls for tools and know-how which transport firms does not by (sic) usually have at their disposal.